Understanding the genetic basis of morphological evolution: the role of homeotic genes in the diversification of the arthropod bauplan.

Due to the segmental organization of their body plans, arthropods can be considered the paradigmatic modular organisms. In the past two decades, genetic studies of the homeotic (Hox) genes in Drosophila melanogaster have provided initial insight into the molecular mechanisms that govern the establishment of segmental identity. In this review, we will address the question of the possible role of four Hox genes: labial (lab), proboscipedia (pb), Deformed (Dfd), and Sex combs reduced (Scr) in the morphological evolution of arthropods, particularly with respect to the evolution of the head and head structures in insects. Overall, these preliminary studies illustrate the role that some of the Hox genes expressed in the insect head have played in the morphological evolution of hexapods and likely arthropods in general.